The report looks at the commute and transit patterns of people in cities and towns around the US. The biggest takeaway is that Americans today are driving less than they did eight years ago, relative to population averages.

But as researcher Chris McCahill at the State Smart Transportation Intiative notes, that trend differs by age group and income. Since 2009, driving among millennials has actually increased, but only for those who earn less than $50,000.

This could be bad news for luxury car brands, since the young people who are driving more are likely not able to afford their vehicles. Those who can afford expensive cars are driving less than they did at the turn of the 21st century. It's unclear whether luxury brands are seeing any effects on their sales. From November 2016 to November 2017, Mercedes' sales were down 1.7%, BMW sales dropped 3.2%, and Lexus sales decreased by 7%. But 2015 and 2016 were record sales years.

As you can see in the graph below, the percentage of people ages 26 to 33 who make more than $100,000 (in blue) declined sharply from 2001 to 2017. Compared to recession levels in 2009, medium-income millennials also drive less today, but only by a few percentage points. Driving among lower-income millennials has slightly surpassed 2001 levels.

Driving trends among American millennials from 2001 to 2017. SSTI The data makes sense. Young people — especially those who are higher-income — are increasingly moving to cities at a growing rates. As City Observatory notes, the number of 25 to 34-year-olds with college degrees in large cities is growing five times faster than the overall population growth in those cities. Urban areas tend to have better access to public transportation, and thus lower levels of car dependence. If young people live in a town without a reliable subway or bus system, they're more likely to drive.

Fewer Americans are also getting their driver's licenses than decades past. According to a 2016 study by the University of Michigan Transportation Research Institute, the percentage of people with a driver's license decreased across all age groups between 2011 and 2014. The trend is most evident among teens. (In 2014, only 24.5% of 16-year-olds had a license, a 47% drop from 1983.)

Even non-luxury car companies have struggled to attract millennials in recent years, and many have invested resources in marketing to them. GM once hired consultants from MTV to find out what the kids are into these days. In collaboration with the car-sharing company Zipcar, Ford has planted its cars on college campuses to help popularize them. In late 2017, Honda debuted an ad arguing that millennials are not #Adulting until they buy a Civic.

If ridership levels for public transit continue to rise, it will become even more important for cities (and their outlying suburbs) to improve their offerings.